A micelle is an aggregate of surfactant molecules (typically organic molecules that are amphiphilic, meaning that they have a hydrophobic or lipophobic end and a hydrophilic or lipophilic end) dispersed in a liquid colloid. Micelles are often spherical or globular in shape, but can adopt other shapes such as shells, vesicles, clusters, bi-layers, cylinders and ellipsoids.
Micelle formation is affected by several factors. However, micelles will only form by themselves in a process of self-assembly when the concentration of the surfactant is greater than a minimum limit known as the critical micelle concentration (CMC). The CMC can be measured by known phase-change monitoring techniques such as absorption or scattering of radiation.
Nanotubes can be defined generally as substantially tubular structures with a diameter on the nanoscale, for example less than 100 nm. They are typically made from atomic carbon bonded in a sp2 structure, although they have been made from other species. The present invention can include single- and multi-walled nanotubes, coated nanotubes, nanotubes that are open-ended and nanotubes that have one or both of their ends closed.
It is known to functionalise nanotubes and attach drug molecules to the nanotubes for use in drug delivery in the human body. However, the area of functionalisation is not controlled, resulting in a variety of nanotubes with molecules attached in random locations. These nanotubes cannot form micelles.